1. Field of the Invention
The invention described herein is directed to a fluid delivery system comprising a fluid pumping device and an associated drive system for continuous fluid delivery applications in medical diagnostic and therapeutic procedures wherein one or more fluids are infused/injected into a patient.
2. Description of Related Art
In the medical field, fluid delivery devices used to provide fluids to patients are generally well-known and exist in many different forms. A system commonly used for this purpose is a gravity-feed system wherein a fluid containing bag is supported above the level of the patient's body and wherein the flow rate to the patient is controlled by the gross pressure of a clamp upon the flexible tube extending between the bag and the patient. It will be readily apparent that the flow rate of fluid through the tube is a function of the amount of constriction of the tube. Manually operated devices are known in the medical field for delivery of fluid under pressure to a patient. Examples of such manually-operated pumping devices are known from U.S. Pat. No. 3,464,359 to King et al.; U.S. Pat. No. 2,062,285 to Bergman; and U.S. Pat. No. 1,748,810 to Wandel, as examples.
Syringe-based infusion pumps and peristaltic pumps have also been used in the medical field for delivering fluids to patients under pressure and provide more precise control over the flow rate and volumetric delivery of fluids to patients. An example of a syringe pump adapted to deliver fluid to a patient is described in U.S. Pat. No. 5,529,463 to Layer et al., which discloses a multi-syringe pump for this purpose. A peristaltic pump system suitable for delivering a constant flow of fluid under pressure to a patient is described in U.S. Pat. Nos. 6,558,125 and 6,488,660, both to Futterknecht.
There are a number of medical procedures which require the delivery of fluids to a patient in a precisely controlled manner. One such application involves the delivery of contrast media fluid to a patient during a diagnostic computed tomography (CT) scan to provide enhanced x-ray images. Traditionally, such contrast media fluid has been delivered to the patient using a syringe-based injection system. Such injection systems require the contrast media fluid to be transferred from its original container to a disposable syringe. The injection system then pressurizes the fluid within the syringe to deliver the fluid to the patient at a controlled flow rate, precisely when needed. Some syringe-based injection systems are capable of accommodating two separate syringes to facilitate sequential or simultaneous delivery of two different types of fluid.
One limitation of a syringe-based fluid injection system is the need to refill and replace the disposable syringes prior to each patient procedure. U.S. Pat. No. 5,806,519 to Evans, III et al. describes a fluid delivery system which could be used to deliver fluid to multiple patients in succession without the need to refill and replace syringes for each patient. Another fluid delivery system that purports to overcome this limitation is disclosed in U.S. Pat. Nos. 6,558,125 and 6,488,660 (Futterknecht). These latter patents disclose a fluid delivery system that utilizes a peristaltic pump to deliver fluid directly from contrast media bottles to the patient. While this system eliminates the need to replace disposable syringes after each patient, the use of a roller-type peristaltic pump inherently limits the pressure capability of the system to approximately 200 psi. Unfortunately, many CT procedures and virtually all angiographic procedures require fluid to be delivered at higher pressures.
In order to provide more precise control of flow rates and volumetric delivery of fluids to patients, positive displacement pump platforms have been developed in the medical field. These devices eliminate the use of syringes and provide increased pressure ranges over peristaltic pumps. One such positive displacement pump device is disclosed in U.S. Pat. Nos. 5,196,197 and 6,197,000 to Reilly et al., which describe a system for the continuous delivery of contrast media fluid to a patient that uses a cam-driven multi-piston pump. Such a pump is capable of delivering fluids at relatively high pressures in a controlled manner. Another example of a positive displacement pump platform intended for use in delivering fluid to a patient undergoing a medical procedure is disclosed in International Publication No. WO 2006/056828, which discloses a volumetric pump with reciprocating and rotating pistons that are adapted to deliver a controlled and continuous flow rate of fluid during a medical procedure. Japanese Publication Nos. JP 61-42199 and JP 61-4220, both assigned to Nemoto Kiyourindou KK, disclose another multi-piston cylinder pump which enables the controlled and continuous delivery of fluids during a medical procedure.
Examples of positive displacement pumps for non-medical applications are well-known. For example, U.S. Pat. No. 5,961,303 to King and U.S. Pat. No. 3,168,872 to Pinkerton disclose positive displacement pumps that comprise rotational and reciprocally operable pistons. Other non-medical positive displacement pumps are known that comprise multiple working pistons for dispensing fluids such as U.S. Pat. No. 5,639,220 to Hayakawa which discloses an “ink” pump with two pistons; Japanese Reference No. JP 4-241778 to Takashima et al. which discloses an automatic metering device for a viscous fluid that utilizes multiple pistons; and U.S. Pat. No. 4,405,294 to Albarda which discloses a dosing pump with two pistons. An older example of a positive displacement pump with multiple pistons is disclosed in U.S. Pat. No. 1,689,419 to Bronander. All of the foregoing listed patents and publications are incorporated herein by reference in their entirety.
In order to provide more precise control of flow rates and volumetric delivery of fluids to patients, positive displacement pump platforms have been developed in the medical field. These devices eliminate the use of syringes and provide increased pressure ranges over peristaltic pumps. One such positive displacement pump device is disclosed in U.S. Pat. Nos. 5,916,197 and 6,197,000 to Reilly et al., which describe a system for the continuous delivery of contrast media fluid to a patient that uses a cam-driven multi-piston pump. Such a pump is capable of delivering fluids at relatively high pressures in a controlled manner. Another example of a positive displacement pump platform intended for use in delivering fluid to a patient undergoing a medical procedure is disclosed in International Publication No. WO 2006/056828, which discloses a volumetric pump with reciprocating and rotating pistons that are adapted to deliver a controlled and continuous flow rate of fluid during a medical procedure. Japanese Publication Nos. JP 61-42199 and JP 61-42200, both assigned to Nemoto Kiyourindou KK, disclose another multi-piston cylinder pump which enables the controlled and continuous delivery of fluids during a medical procedure.
Another disadvantage present in the foregoing positive displacement pump examples, particularly multi-piston positive displacement pumps, is that as the pistons in multi-piston positive displacement pumps sequentially deliver pressurized fluid to the pump outlet, there are fluctuations or “pulsatility” in the flow rate as the fluid source transitions from one piston to the next. This pulsatility can be reduced with the inclusion of additional pistons but can never be completely eliminated. Moreover, multi-piston pumps often include passive check valves and like devices which are used to direct fluid into and out of piston chambers. Such passive valves are often unable to respond quickly enough at high cycle rates and this can lead to volumetric inefficiencies and leakage at high pressures.